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Why sauropods had long necks



From: Ben Creisler
bcreisler@gmail.com


This new open-access online paper has not been mentioned yet:


Michael P. Taylor & Mathew J. Wedel (2012)
Why sauropods had long necks; and why giraffes have short necks.
http://arxiv.org/abs/1209.5439
http://arxiv.org/ftp/arxiv/papers/1209/1209.5439.pdf

The necks of the sauropod dinosaurs reached 15 m in length: six times
longer than that of the world record giraffe and five times longer
than those of all other terrestrial animals. Several anatomical
features enabled this extreme elongation, including: absolutely large
body size and quadrupedal stance providing a stable platform for a
long neck; a small, light head that did not orally process food;
cervical vertebrae that were both numerous and individually elongate;
an efficient air-sac-based respiratory system; and distinctive
cervical architecture. Relevant features of sauropod cervical
vertebrae include: pneumatic chambers that enabled the bone to be
positioned in a mechanically efficient way within the envelope; and
muscular attachments of varying importance to the neural spines,
epipophyses and cervical ribs. Other long-necked tetrapods lacked
important features of sauropods, preventing the evolution of longer
necks: for example, giraffes have relatively small torsos and large,
heavy heads, share the usual mammalian constraint of only seven
cervical vertebrae, and lack an air-sac system and pneumatic bones.
Among non-sauropods, their saurischian relatives the theropod
dinosaurs seem to have been best placed to evolve long necks, and
indeed they probably surpassed those of giraffes. But 150 million
years of evolution did not suffice for them to exceed a relatively
modest 2.5 m.